Sorry for the sarcasim. If you are looking in cow fields you are more than likely after psilocybe cubensis. Yes, it is preferred to search for the after rain or during high humidity. They will not be found under the cow shit, they will be found sprouting directly up from cow shit and no where else. Even if it appears there is no cow shit where you may find one, there is, its in the soil. The mushroom you're looking for will look something like this. This is not my picture, I have to give credit to my friend GGreat234, he takes pictures of these beautiful mushrooms, just pictures of course. They are native to his state of Florida.
[This message has been edited by Lizard King (edited January 12, 2000).]